The genetic modification of T lymphocytes is the basis for novel approaches to study and establish tumor[unreadable] immunity. The genetic transfer of antigen receptors is indeed a powerful approach to rapidly generate tumorspecific[unreadable] T lymphocytes. However, while necessary, tumor antigen recognition is not sufficient to permit tumor[unreadable] eradication. To achieve this goal, primed CTLs must expand to sufficient numbers, migrate to tumor sites,[unreadable] mature into effector cells and carry out their cytolytic function unimpeded. The genetic strategies we are[unreadable] pursuing aim to increase recognition of tumor antigens, enhance anti-tumor functions and sustain T cell[unreadable] function in cancer patients. Most important for our understanding of human tumor immunology and[unreadable] therapeutic goals, gene addition and knockdown strategies can be applied to human T lymphocytes, on[unreadable] which we focus in this project. The specific aims are based on our published and preliminary data. Aim 1: To[unreadable] investigate the biological properties and therapeutic potential of tumor specific CD8+ T cells co-stimulated by[unreadable] CD28 and 4-1BB. We hypothesize that concerted CD28 and 4-1BB signals sustain CD8+ T cell proliferation[unreadable] and survival, and may thus augment the therapeutic potency of genetically targeted T lymphocytes. Aim 2:[unreadable] To investigate the effect of ex vivo IL-15 on the proliferation, survival, differentiation and therapeutic potential[unreadable] of adoptively transferred human primary T lymphocytes. This aim builds on our recent finding that IL-15[unreadable] enhances the therapeutic potential of cultured 19z1-transduced PBLs upon adoptive transfer to tumorbearing[unreadable] mice. We hypothesize that IL15 increases therapeutic efficacy through several mechanisms, most[unreadable] importantly T cell survival. Aim 3: To establish an efficient protocol for T'cell transduction and expansion in a[unreadable] closed system and perform a phase I clinical trial to assess the safety, persistence and therapeutic activity of[unreadable] autologous 19-28z-transduced T lymphocytes in patients with relapsed, chemo-refractory chronic[unreadable] lymphocytic leukemia. We hypothesize that patient T cells expressing a CD28/ -like chimeric antigen[unreadable] receptor will induce durable remissions, more so in cyclophosphamide-treated recipients. Our investigation[unreadable] critically depends on the Gene Transfer and Somatic Cell Engineering Core, to genetically modify patient T[unreadable] cells, the Imaging Core, to study T cell migration and persistence in vivo, and the Administrative Core, for[unreadable] biostatistics and data management.